From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263151AbTJQRXK (ORCPT ); Fri, 17 Oct 2003 13:23:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263203AbTJQRXK (ORCPT ); Fri, 17 Oct 2003 13:23:10 -0400 Received: from tmr-02.dsl.thebiz.net ([216.238.38.204]:15112 "EHLO gatekeeper.tmr.com") by vger.kernel.org with ESMTP id S263151AbTJQRXH convert rfc822-to-8bit (ORCPT ); Fri, 17 Oct 2003 13:23:07 -0400 Date: Fri, 17 Oct 2003 13:07:46 -0400 (EDT) From: Bill Davidsen To: Andre Tomt cc: =?ISO-8859-1?Q?M=E5ns_Rullg=E5rd?= , linux-kernel@vger.kernel.org Subject: Re: Software RAID5 with 2.6.0-test In-Reply-To: <1065690658.10389.19.camel@slurv> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 9 Oct 2003, Andre Tomt wrote: > On Thu, 2003-10-09 at 10:55, Måns Rullgård wrote: > > > Was this a 4 port or 2 port HPT controller? Keep in mind, two disks on > > > the same IDE channel severely degrades performance, *especially* with > > > RAID. > > > > It's a four port SATA controller. I'd never even think about placing > > two disks on the same cable. > > You can't either, considering it is SATA :-) > > However, I wouln't count on superior performance from software based > RAID 5 (ata/fakeraid or otherwise), that is whats real raid controllers > are for. While an overloaded system may benefit from offloaded the CPU requirements of RAID, unless you go to a very expensive external unit the kernel RAID will usually outperform the inexpensive RAID embedded on a controller. The kernel simply knows more about the data needs and can can do things a controller can't. You can also use only part of a drive, by partition, in a RAID group, leaving the rest to be used as dumb disk. Very cost effective, if only a part of the data justified mirroring, you don't need to mirror whole drives. Yes, that's a cost vs. speed tradeoff, but an effective one where reliabiity is needed, but performance is not critical. -- bill davidsen CTO, TMR Associates, Inc Doing interesting things with little computers since 1979.